title: Three-dimensional axon morphologies of individual layer 5 neurons indicate cell type-specific intracortical pathways for whisker motion and touch.
abstract: The cortical output layer 5 contains two excitatory cell types, slender- and thick-tufted neurons. In rat vibrissal cortex, slender-tufted neurons carry motion and phase information during active whisking, but remain inactive after passive whisker touch. In contrast, thick-tufted neurons reliably increase spiking preferably after passive touch. By reconstructing the 3D patterns of intracortical axon projections from individual slender- and thick-tufted neurons, filled in vivo with biocytin, we were able to identify cell type-specific intracortical circuits that may encode whisker motion and touch. Individual slender-tufted neurons showed elaborate and dense innervation of supragranular layers of large portions of the vibrissal area (total length, 86.8 ± 5.5 mm). During active whisking, these long-range projections may modulate and phase-lock the membrane potential of dendrites in layers 2 and 3 to the whisking cycle. Thick-tufted neurons with soma locations intermingling with those of slender-tufted ones display less dense intracortical axon projections (total length, 31.6 ± 14.3 mm) that are primarily confined to infragranular layers. Based on anatomical reconstructions and previous measurements of spiking, we put forward the hypothesis that thick-tufted neurons in rat vibrissal cortex receive input of whisker motion from slender-tufted neurons onto their apical tuft dendrites and input of whisker touch from thalamic neurons onto their basal dendrites. During tactile-driven behavior, such as object location, near-coincident input from these two pathways may result in increased spiking activity of thick-tufted neurons and thus enhanced signaling to their subcortical targets.
authors.affiliation: Digital Neuroanatomy, Max Planck Florida Institute, Jupiter, FL 33458-2906, USA. marcel.oberlaender@maxplanckflorida.org
authors.forename: Marcel
authors.initials: M
authors.lastname: Oberlaender
authors.forename: Zimbo S R M
authors.initials: ZS
authors.lastname: Boudewijns
authors.forename: Tatjana
authors.initials: T
authors.lastname: Kleele
authors.forename: Huibert D
authors.initials: HD
authors.lastname: Mansvelder
authors.forename: Bert
authors.initials: B
authors.lastname: Sakmann
authors.forename: Christiaan P J
authors.initials: CP
authors.lastname: de Kock
mesh_terms: D000200:Action Potentials; D000818:Animals; D001369:Axons; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar; D014738:Vibrissae / Q000502:physiology*